1. Field of the Invention
This invention relates to a subsurface well tool for use in oil and gas wells for injecting fluids into perforations of a production formation traversed by the well casing; more specifically, to a well tool mechanically set by axial manipulation of the tubing string and providing for pressure equalization across packing elements on opposite sides of a selected group of perforations and additionally effecting pressure equalization between the well annulus and the bore of the tubing string carrying the tool by rotation of the tubing string to facilitate release of the well too from its set condition.
2. Description of the Prior Art
It is often necessary to inject fluids, such as water, acid or various types of chemicals, into an underground formation through perforations in the casing which provide for communication between perforations in the formation and the bore of the casing. Most conventional tools used to inject fluids into a selected vertical group of perforations contained within a specified interval of the well require the use of two tools, suspended in series by a tubing string, one above the interval and one below the interval, and connected together to permit fluid injection. Thus, an upper packer can be secured to a ported tubing section which is in turn secured to a lower packer, thus providing isolation for the intermediate interval.
These tools are suitable only for injecting fluids into intervals of six feet or greater height. Prior art tools are not suitable for injecting fluids into selected intervals as small as six inches in vertical height, which may be desirable if fluids must be selectively injected into a single or closely adjacent well perforations. The conventional multipacker device is unsuitable for use in injecting fluids into such small intervals because the mechanism necessary to set each packer renders it virtually impossible to position the packers closely adjacent each other.
In the above identified co-pending application, an injection tool is disclosed wherein a plurality of vertically spaced packing elements are actuated by axial movements of a common mandrel traversing the bore of the packer body that mounts the packing element. For optimum efficiency, it is desirable to selectively open and close a recirculation or equalization fluid passage between the bore of the tubing string and the casing annulus above the upper most tool, and the provision of such apparatus in combination with the injection tool of the above-identified application is the object of the instant invention.